NAME
pthread_exit —
thread termination
SYNOPSIS
#include
<pthread.h>
void pthread_exit(void *value_ptr);
DESCRIPTION
The pthread_exit () function shall
terminate the calling thread and make the value value_ptr
available to any successful join with the terminating thread. Any
cancellation cleanup handlers that have been pushed and not yet popped shall
be popped in the reverse order that they were pushed and then executed.
After all cancellation cleanup handlers have been executed, if the thread
has any thread-specific data, appropriate destructor functions shall be
called in an unspecified order. Thread termination does not release any
application visible process resources, including, but not limited to,
mutexes and file descriptors, nor does it perform any process-level cleanup
actions, including, but not limited to, calling any
atexit(3) routines that may exist.
An implicit call to pthread_exit
() is made when a thread other than the thread in which
main () was first
invoked returns from the start routine that was used to create it. The
function's return value shall serve as the thread's exit status.
The behavior of pthread_exit () is
undefined if called from a cancellation cleanup handler or destructor
function that was invoked as a result of either an implicit or explicit call
to pthread_exit ().
After a thread has terminated, the result of access to local
(auto) variables of the thread is undefined. Thus, references to local
variables of the exiting thread should not be used for the
pthread_exit () value_ptr
parameter value.
The process shall exit with an exit status of 0 after the last thread has been terminated. The behavior shall be as if the implementation called exit(3) with a zero argument at thread termination time.
RETURN VALUE
The pthread_exit () function cannot return
to its caller.
ERRORS
No errors are defined.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
The normal mechanism by which a thread terminates is to return
from the routine that was specified in the
pthread_create(3) call that started it. The
pthread_exit () function provides the capability for
a thread to terminate without requiring a return from the start routine of
that thread, thereby providing a function analogous to
exit(3).
Regardless of the method of thread termination, any cancellation cleanup handlers that have been pushed and not yet popped are executed, and the destructors for any existing thread-specific data are executed. This volume of POSIX.1-2008 requires that cancellation cleanup handlers be popped and called in order. After all cancellation cleanup handlers have been executed, thread-specific data destructors are called, in an unspecified order, for each item of thread-specific data that exists in the thread. This ordering is necessary because cancellation cleanup handlers may rely on thread-specific data.
As the meaning of the status is determined by the application (except when the thread has been canceled, in which case it is PTHREAD_CANCELED), the implementation has no idea what an illegal status value is, which is why no address error checking is done.
FUTURE DIRECTIONS
None.
SEE ALSO
exit(3), pthread_create(3), pthread_join(3)
XBD <pthread.h>
CHANGE HISTORY
First released in Issue 5. Included for alignment with the POSIX Threads Extension.
Issue 6
The pthread_exit () function is marked as
part of the Threads option.
Issue 7
The pthread_exit () function is moved from
the Threads option to the Base.